Hi All,

Apologies for the long post but I need some recommendations. Please keep in mind that I am in New Zealand, and these trucks are not common here.
I have a weird problem with my 97 5.7 Vortec 4L60E (151,000 mi), wanting to know if anyone else has had the same issues.

When cold, it will shift from 1-2 hard, then to 3rd. Then it is in limp mode. 3rd only, manual shift to 2nd. I can switch the truck off, and it does the same over again.

Once it has warmed up (110 on the temp gauge) and the truck is switched off/restarted, all is good - shifting fine, kickdown all good, working well.

If it was a short in the wiring, I would expect it to be unaffected by temperature, and therefore consistently failing.

I have replaced the ignition switch & wiring, and the throttle position sensor, and this has not had any effect on the issue.

I plan to replace shift a&b solenoids, but I suspect the 3-2 solenoid maybe the issue.

Any info would be appreciated.

OBD2 codes are:
P0122 - Throttle/Pedal Position Sensor/Switch "A" Circuit Low
P0327 - Knock Sensor 1 Circuit Low Bank 1 or Single Sensor
P0785 - Shift Timing Solenoid "A"
P1351
P1860